LEAF-CUTTING CATERPILLAR. 19 



insect consists in maintaining this strip of leaf 

 in its spiral form, which would otherwise natu- 

 rally unwind by its own weight, and flutter in 

 the wind as a torn fragment. Here it is that 

 silk is again skilfully employed. The caterpillar 

 commences much as other leaf-rolling insects 

 do, by fastening a thread to the edge of the 

 leaf and drawing it towards the desired point. 

 But as the work proceeds the insect generally has 

 three skeins or bands of silk extended from the 

 opening of its case to the leaf. The first is the 

 shortest and the most direct, issuing from the 

 interior of the roll ; the second is fastened to 

 the middle of the last spiral, and extends to the 

 leaf; the third is more extensive still, and all 

 three are admirably disposed for keeping the leaf 

 bent to the proper form. These skeins are com- 

 posed of a great number of threads parallel with 

 each other, which not only serve to retain the leaf 

 in its spiral form, but also serve the caterpillar as 

 a kind of ladder, by which it mounts, and on which 

 it rests while cutting out fresh portions of leaf. 

 It sometimes happens accidentally to this cater- 



